In the bio-pharmaceutical industry, there is a particular need to provide sanitary fittings on bioprocessing (BPE) equipment. More particularly, mechanical seals for such equipment may have fluid lines connected thereto which supply pressurized fluid used in the mechanical seal to help prevent leakage of product and process fluid along a shaft, such as a pump. In this regard, it is important that the fittings for the fluid handling equipment do not allow entry of contaminants into the flow of product and process fluid. Due to the clean environment in which these mechanical seals are used, the fittings are referred to as sanitary fittings. For example, in fluid-pressurized mechanical seals used in the bio-pharmaceutical marketplace, it has become necessary to eliminate standard threaded fittings in seal housings of this type, since threaded fittings can trap contaminants and may be difficult to clean or even be unclean-able.
Therefore, it is known to replace drilled and tapped holes on seal housings with welded sanitary fittings, which are welded to the seal housing and permit the connection of fluid lines to the seal for pressurizing the seal with a seal fluid. However, the welded fittings must meet stringent weld requirements as set forth in established standards such as the ASME BioProcessing Equipment (ASME BPE) Standard.
In one known practice, the sanitary fittings are ferrules welded to a length of tube, wherein the ferrule and a 0.5 inch tube are welded using an orbital welder, and then the surfaces of the weld, internally and externally, are machined to a fine surface finish consistent with the rest of the component. The welded assembly in turn is welded to a seal housing. The interior of the tubing is honed to improve the surface finish around the weld and the weld is inspected internally and externally.
Once welding, honing, and inspection are completed and the piece is found to meet current quality requirements, it is sent to be electropolished and/or passivated, wherein the electropolish must pass inspection of the housing. While the final structure works adequately, the welding of the fittings to the seal housings can prove difficult since the housing must be prepared for welding by machining to precise design standards. The fitting must be prepared for welding by cutting it to the proper length and beveling the tubing to accurately fit to the housing. The tubing must be fit to the housing and held in place while welding takes place. The welding is particularly difficult because of the room available, the fact that no filler may be added, it must be a full penetration weld, and a slight shake of the welder's hand will cause a ‘burn’ on the housing.
If electropolishing exposes problems with the weld, the housing must be scrapped or re-machined, and if re-welding the piece is required, it must again go through the electropolishing and/or passivation step.
In view of the foregoing, it is an object of the invention to provide an improved sanitary fitting for mechanical seals and other fluid handling equipment, particularly when used in the BPE industry.
The invention relates to a threaded sanitary fitting which eliminates the use of welds while meeting the requirements of established standards including the ASME BPE Standard. The threaded sanitary fitting can be screwed into a socket in the seal or equipment housing and still maintains a cleanable and sanitary joint as required by the ASME BPE standards. Normally, a screwed in fitting is not considered cleanable because of the shape of the gasket groove and the exposure of threads to contaminants, which can be held within the threads. The inventive fitting overcomes such difficulties since a non-threaded tubular insert is fitted into a receiver socket and includes a gasket and fastener construction, which secures the tube insert within the socket by threads but prevents passage of contaminants between the fluid passage and the exterior of the tube insert where the threads are located.
More particularly, the threaded socket is formed in the equipment housings or other structure to which the insert will be connected. The sanitary fitting includes an elongate tubular insert, which has a main tubular section, which is cylindrical and terminates at an annular flange or annulus which seats at the bottom of the socket. The bottom face of the annulus includes a groove, which receives a gasket that is compressed between the annulus and bottom face of the socket to prevent entry of fluids into this space. A threaded wall of the socket is spaced outwardly of the smooth-surfaced insert so as to receive an externally-threaded nut within such space. The nut is slid down the fitting and engaged with the socket threads wherein the nut abuts against a top face of the annulus and drives the fitting insert into and retains the insert tightly therein.
When the nut is screwed in and tightened, the o-ring at the annulus bottom extrudes inwardly toward the interior passage defined by the interior diameter of the tubular insert and the housing bore formed in the seal housing. This compression of the O-ring axially deforms and radially widens the O-ring to minimize any crevice at the joint between the insert and socket, which crevice could otherwise create a pocket that would retain fluid when the rest of the system is drained.
At the top of the nut, a secondary o-ring is provided to seal the threads from atmospheric dirt and debris. Since the hex nut and tubular insert are separate pieces the tubing can be bent to an angle and held in proper position while the nut is tightened.
The advantages of this fitting include: no additional machining preparation on the existing housings; the fitting can be supplied pre-welded and electropolished; o-rings can be installed so that assembly only requires threading in of the nut; no BPE welding is required at a manufacturer; bent or damaged tubes or wrong lengths can be replaced with no damage to housing; a housing can be electropolished once without interference of welded fittings; housings and fittings can be more accurately and quickly inspected; shipping containers can be smaller (if a mechanical seal is shipped without the fittings installed.
Other objects and purposes of the invention, and variations thereof, will be apparent upon reading the following specification and inspecting the accompanying drawings.
Certain terminology will be used in the following description for convenience and reference only, and will not be limiting. For example, the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the arrangement and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.